Convergence finder for threedimensional cameras



United States Patent Ofi tice Patented Apr. 26, 1955 CONVERGENCE FINDER FUR THREE- DIMENSIONAL CAMERAS John P. Kiel, Jr., Van Nuys, Calif., assigner to Edward Furet, Burbank, Calif.

Application August 11, 1953, Serial No. 373,501 Claims. (Cl. 95-18) The present invention relates generally to the field of photography and more particularly to an improved convergence finder for use with a pair of three-dimensional cameras.

in filming three-dimensional motion pictures or in taking three-dimensional television programs, a pair of camutilized, provide a related pair of images which cooperate in affording a stereoscopic image. lt is common practice to mount the cameras upon a wheeled carriage commonly termed a `dolly whereby such cameras may be moved relative to the subject being photographed. Where the dolly is moved during the taking of a scene, a so-called "dolly shot results. When taking a dolly shot, it is advisable that the two cameras always remain converged on the principal subject being photographed in order that a clear picture will result. This is likewise true where the subject or subjects move relative to the cam- Prior to the development of the present invention, it was extremely ditiicult to obtain an indication as to whether or not the pair of cameras were actually in convergence. The conventional manner of providing such an indication requires that workmen the scene. but also often results in error. is generally possible to retake the scene, such retakes result in added expense, Furthermore, if take live television programs utilizing a pair of threedimensional cameras, no retakes are possible.

It is a major object of the present invention to provide a novel convergence finder for use with a pair of three-dimensional cameras.

Another object of the invention is to vergence finder which may be constructed as part of the camera supporting structure in the form of a complete self-contained of any other elements between ject being photographed.

A further object of vergence find of the present invention to provide a convergence finder which is simple in design and .ruggd of construction whereby it may have a long service ie.

It is another object to provide a convergence finder which is especially adapted for use with a pair of cameras having means for adjusting the interocular distance therebetween.

An additional object is to provide a convergence finder of the aforedescribed nature having but a few working parts whereby it may be constructed of readily obtainable materials and manufactured at a comparatively low cost.

These and other objects of the present invention will become apparent from the following detailed description of a preferred embodiment thereof, when taken in conjunction with the appended drawings wherein:

Figure l is a top plan View sional cameras equipped with bodying the present invention;

Figure 2 is an enlarged fr of F view taken on line 2-2 Figure 3 is an enlarg View taken on line 3`3 o Figure 4 is an enlarg view taken on line 4 4 o igure agmentary, vertical sectional fragmentary vertical sectional f Figure l;

fragmentary vertical sectional f Figure l;

Figure 5 is a diagrammatic view showing the mode of operation of said converg Figure 6 is an enlar tional View taken on line Figure 7 is a fragmenta modification of said co Referring to the drawin thereof, there is shown mounted a ence finder;

ged fragmentary horizontal sec- 6*6 of Figure 3; and ry perspective view showing a nvergence finder.

pair of cameras F fixed against rotation relative t vergence by manipulation side of the base member.

forwardly of crank C on the gs and base particularly to Figure l member B whereon are dolly rela- Same ber is adapted to effect movement toward or away from the vary the interocular distan The preferred form semi-transparent mirror mounted at one si distance ahead of the ca but a single image of sa sight 24, separate images of said ator.

With regard to a mo lf the camer side of the base memof the fixed camera F movable camera M so as to ce therebetween.

convergence finder embodying the present invention includes a first semi-reflecting,

20 rigidly mounted at the front ect ima ting type reflecting type. 2t) is so located relative and a sight 24 de of the base member B. The first mirror 20 is of the seini-refiec while the sec- The first mirror to the fixed camera F and the ges lying upon the opof this camera into the sight.

The mirrordesigned that the second mirror meras, the operator id subject when looking into the as are not converged, however, subject will re particular the optical will observe e seen by the operaforementioned device, and referring to Figures l and 4, the

base member B, as by bolts 32.

a depending is slidably received between a extending guides 3i secured to the The midportion of the bore 33 having threads that are engaged by external threads 36 formed on a longitudinally extending member.

be moved toward or awa to vary the interocular own in Figure 2 cranl This crank rod nde i rod 38 verticall journalled by the base movable camera M istance therebetween.

arcanes end of the post 40 below a washer S4, which nut is secured by a cotter pin 56.

A second vertically extending post S depends from the underside of the camera M rearwardly of the pivot post 40. This second post formed in the base member. is of reduced diameter, may pivotally receive a also formed with nut 68 adapted to retain the lug The lug 64.

58 extends through a slot 60 lower part of post 5 8 as indicated at 62, whereby `1t This lower portion 1s external threads 66 for receiving a 64 in place. The opposite end of the lug 64 is formed with a socket portion 70 having internal threads adapted for engagement with external threads 72 formed upon 74. The opposite end of the rod 7 arm 76 by means of a universal arm 76 is journalled to the base member With this arrangement, rotation to the crank C.

the free end of a rod 4 is coupled to a crank joint 78. The crank B and is keyed of the crank C will effect concurrent rotation of crank arm 76 and rod 74 whereby the latter will be threaded into or out of the socket portion 70 of the lug 64 depending upon the direction in which the crank is being rotated, m effect,

shortening or lengthening the rod the camera post 40 upon Turning now to the mirrors of the cameras F and M, respectively, is at and is coated on its front surface M will be caused to rotate rotation of the crank C.

and 22 mounted m front 74. In this manner,

about the pivot the first mirror 20 with a reiiecting material in such a manner that the mirror is semi-reflective and semi-transmissive.

This mirror is rigidly secured at its lower edge within a slot 80 formed in a forwardly extending plate 82, to the front of should be noted that this mirror the axis of the6lens but spaced below,

Referring to Figures 2, 3 and is aligned with, but spaced below,

of the camera M. This second mirror at its lower edge within a slot 86 formed S8, which eleme within a bore 90 turning element that is journaled which plate is rigidly the camera F as shown in Figure mounted 4. It 20 is aligned with, 84 of camera F.

the second mirror 22 the axis of the lens 85 is rigidly secured in a mirror nt includes a disc S9 formed in a forwardly extending plate 92 for rotation relative thereto about a vertical axis. The rear of the plate 92 is rigidly aihxed to the front of the camera M. A post 94 formed with external threads 96 depends from the disc 89. This post 94 ts within tudinally extending rod 100 and is by a nut 102. ably supported by a guide in turn rigidly connected to B opposite the As shown clearly in Figure 6, 88 includes a rearwardly and tongue 108, which tongue is This slot serves to pivotally interconnect a 116. These links are of connected at their distal ends by a bore 93 formed at one end of a longirotatably held therein the rod 100 is slidelement or collar 104 that is the side of the base member cranks C and I by means of a support 106. mirror turning element sidewardly extending formed with a slot 110. 110 slidably receives an upstanding pin 112 that pair of links 114 and equal length and are pivotally pins 118 and 120, re-

spectively, to the rod 100 and to the plate 92, respec- The distal ends of these tively.

from the axis of r equal distances With this arrangement, and Figure 5, if it is assumed that the first photographing a subject or scene whereby the optical axes of at some dlstance therefrom,

links are located at otation of element 88.

referring particularly to cameras F and M are that is disposed the lenses S4 and 85 thereof are disposed in a generally parallel relationship,

should it become desirable to shift to a close-up of the subject, it is necessary that the camcra M be pivoted in a counterclockwise direction about the pivot post so that its optical optical axis of camera Thus. the optical line AS to line AS.

the camera M by virtue of the connection of this ing element S3, and

of the mlrror controlled by the links 114 and links 114 and 116 are in a counter-clockwise direction, 100 will be pulled to the right relative to the collar 104 .counter-clockwise direction relative ing such movement, the exact number of degrees through which the disc S9 and hence the mirror 22 moves being axis will intersect the F at the location of the subject A'. axis of the lens 85 must be moved from During such pivotal movement of the rod rod to the mirror turnhence to the plate 92. The disc 89 turning element will also be rotated in a to the plate 92 dur- 116. Thus, since the of equal length and have their distal ends mounted at equal distances from the axis of rotation the center line of the ngle between the links.

When the optical axis of the the line AS to the line AS, the links are moved from their dotted position of Figure 5 to their solid line, primed, position thereof, and the angle between the links will be reduced or changed. Since the tongue 108 always bisects this angle between the links, changing this angle by a certain amount will cause the tongue to move through an angle of just half this amount. In this connection, it should be noted that the rod is of such a length that it may be considered as being perpendicular to the optical axis of xed camera F at all times.

Accordingly, since the second mirror 22 is rigidly afiixed to the tongue, it will be rotated through an angle equal to half the angle through which the movable camera M is rotated relative to the base member B and the iixed camera F. This arrangement is necessary in order that the second mirror 22 Will always reect light, originating upon the optical axis of the movable camera, through the first mirror 20 and the sight 24. In this regard, it will be apparent that any change in angularity of a iiat mirror will concurrently effect a change in angularity of the light reected therefrom through double the number of degrees through which the mirror is rotated. This is true because the angle of reiiection of the light being equal to the angle of incidence thereof, the sum of these angles must be added to the angle through which the mirror is rotated.

Although the mirror moving means H shown and described herein, has proved very satisfactory in actual use, it will be apparent that other means for effecting the desired movement of the second mirror 22 may be utilized without departing from the scope of the present. invention. In this regard, while the rod 100, 114 and 116, tongue 108 and upstanding pin 112 function very satisfactorily as a bisector linkage in permitting the second mirror 22 to turn through exactly one-half the angle through which the movable camera is turned, other forms of bisector linkages may be employed for this purpose.

It should be observed that while ideally the second mirror 22 should pivot about the pivotal axis of the movable camera M, practical constructional diiculties may preclude such arrangement. By spacing this mirror 22 slightly forwardly of the movable cameras pivotal axis in the manner disclosed herein, however, very satisfactory results are achieved.

In operation, the operator may be disposed adjacent the cranks I and C with his eye looking into the sight 24. If but a single image of the subject located at the point of focus of the cameras is visible in the sight, the cameras are in convergence. If, however, a double image of this subject is visible, the operator may turn the crank C until the two images are in register. The cameras will then be in convergence.

During a dolly shot when the cameras are being moved toward or away from a subject whereby the point of convergence `is constantly changing, the operator may maintain the cameras in convergence by continually rotating the crank C so as to keep a single image of the subject visible in the sight. The interocular distance between the two cameras may be readily varied by manipulation of the crank I. It should be especially noted that such variation does not affect the method of operation of the convergence finder. The operator need never take his eye from the sight during adjustment of the cranks, and both of the cranks are positioned for ready access by the operator.

Referring now to Figure 7, there is shown a modication of the preferred form of convergence finder. In this modification, the fixed mirror 20a, as well as the movable mirror 22a is of the fully reecting type. However, the fixed mirror 20a reiiects only one-half of the image, such as the loWer half, while the movable mirror 22a reflects the other half. Thus, each of the mirrors 20a and 22a need be only half as high as their counterparts, the mirrors 20 and 22, previously described. By vertically positioning the mirrors 20a and 22a so that both may simultaneously be viewed through the finder 24, the same effect may be obtained as in my previously described form. However, instead of seeing two complete images when the cameras are not properly converged, with this alternate form of my device, the operator will see an upper image, of half the subject, laterally displaced from a lower image of the other half of the subject.

Although camera F is rotated from there has been shown and described what is being pivotally connected to said camera, respectively, from the axis of A convergence nder for use with a xed camera and a movabl ber opposite said sight; a horizontally extending rod rigidly axed at one of its ends camera so as to pivot said reflecting mirror through an said mounted in side-by-side relationship by a base member, said movable camera being pivotable about a vertical axis relative to said fixed camera, said nder comprising: a horizontally disposed sight mounted at one side ase member; a semi-rcecting mirror rgidlymountwhich said movable camera is being rotated whereby said reflecting mire manipulated thereby maintai pivot said reflecting mirror through Y of its ends to said disc and having its opposite end movably disposed Within said collar; a pair of horizontal links of equal length', and, an upstanding pin pivotally interconnecting one end of each of said links, the distal ends of said links being pivotally connected to said rod and to said plate at points located an equal distance from the axis of rotation of said disc, said pin sliding Within said slot during pivotal movement of said movable camera so as to pivot said second mirror through an angle equal to half the angle through which said movable camera is being rotated whereby said second mirror may constantly References Cited in the le of this patent UNITED STATES PATENTS 798,931 staat Sept. 5, 1905 1,356,838 Stein Oct. 26, 1920 2,545,465 Hough Mar. 20, 1951 

